/Engine/Plugins/Runtime/MeshModelingToolset/Source/ModelingOperators/Public/SpaceDeformerOps/TwistMeshOp.h
Copies over the original mesh into result mesh, and initializes ObjectToGizmo in preparation to whatever work the base class does. Note that the function will return if OriginalMesh was null but doesn't have a way to log the error, so the base class should check OriginalMesh itself as well.
virtual void CalculateResult ( [FProgressCancel](API\Runtime\GeometryCore\Util\FProgressCancel) * Progress )